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.\" Modified Sat Jul 24 18:20:12 1993 by Rik Faith (faith@cs.unc.edu)
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.TH SETLOCALE 3  2021-03-22 "GNU" "Linux Programmer's Manual"
.SH NAME
setlocale \- set the current locale
.SH SYNOPSIS
.nf
.B #include <locale.h>
.PP
.BI "char *setlocale(int " category ", const char *" locale );
.fi
.SH DESCRIPTION
The
.BR setlocale ()
function is used to set or query the program's current locale.
.PP
If
.I locale
is not NULL,
the program's current locale is modified according to the arguments.
The argument
.I category
determines which parts of the program's current locale should be modified.
.ad l
.nh
.TS
lB lB
lB lx.
Category	Governs
LC_ALL	All of the locale
LC_ADDRESS	T{
Formatting of addresses and
geography-related items (*)
T}
LC_COLLATE	String collation
LC_CTYPE	Character classification
LC_IDENTIFICATION	T{
Metadata describing the locale (*)
T}
LC_MEASUREMENT	T{
Settings related to measurements
(metric versus US customary) (*)
T}
LC_MESSAGES	T{
Localizable natural-language messages
T}
LC_MONETARY	T{
Formatting of monetary values
T}
LC_NAME	T{
Formatting of salutations for persons (*)
T}
LC_NUMERIC	T{
Formatting of nonmonetary numeric values
T}
LC_PAPER	T{
Settings related to the standard paper size (*)
T}
LC_TELEPHONE	T{
Formats to be used with telephone services (*)
T}
LC_TIME	T{
Formatting of date and time values
T}
.TE
.hy
.ad
.PP
The categories marked with an asterisk in the above table
are GNU extensions.
For further information on these locale categories, see
.BR locale (7).
.PP
The argument
.I locale
is a pointer to a character string containing the
required setting of
.IR category .
Such a string is either a well-known constant like "C" or "da_DK"
(see below), or an opaque string that was returned by another call of
.BR setlocale ().
.PP
If
.I locale
is an empty string,
.BR """""" ,
each part of the locale that should be modified is set according to the
environment variables.
The details are implementation-dependent.
For glibc, first (regardless of
.IR category ),
the environment variable
.B LC_ALL
is inspected,
next the environment variable with the same name as the category
(see the table above),
and finally the environment variable
.BR LANG .
The first existing environment variable is used.
If its value is not a valid locale specification, the locale
is unchanged, and
.BR setlocale ()
returns NULL.
.PP
The locale
.B """C"""
or
.B """POSIX"""
is a portable locale;
it exists on all conforming systems.
.PP
A locale name is typically of the form
.IR language "[_" territory "][." codeset "][@" modifier "],"
where
.I language
is an ISO 639 language code,
.I territory
is an ISO 3166 country code, and
.I codeset
is a character set or encoding identifier like
.B "ISO\-8859\-1"
or
.BR "UTF\-8" .
For a list of all supported locales, try "locale \-a" (see
.BR locale (1)).
.PP
If
.I locale
is NULL, the current locale is only queried, not modified.
.PP
On startup of the main program, the portable
.B """C"""
locale is selected as default.
A program may be made portable to all locales by calling:
.PP
.in +4n
.EX
setlocale(LC_ALL, "");
.EE
.in
.PP
after program initialization, and then:
.IP \(bu 2
using the values returned from a
.BR localeconv (3)
call for locale-dependent information;
.IP \(bu
using the multibyte and wide character functions for text processing if
.BR "MB_CUR_MAX > 1" ;
.IP \(bu
using
.BR strcoll (3)
and
.BR strxfrm (3)
to compare strings; and
.IP \(bu
using
.BR wcscoll (3)
and
.BR wcsxfrm (3)
to compare wide-character strings.
.SH RETURN VALUE
A successful call to
.BR setlocale ()
returns an opaque string that corresponds to the locale set.
This string may be allocated in static storage.
The string returned is such that a subsequent call with that string
and its associated category will restore that part of the process's
locale.
The return value is NULL if the request cannot be honored.
.SH ATTRIBUTES
For an explanation of the terms used in this section, see
.BR attributes (7).
.ad l
.nh
.TS
allbox;
lbx lb lb
l l l.
Interface	Attribute	Value
T{
.BR setlocale ()
T}	Thread safety	MT-Unsafe const:locale env
.TE
.hy
.ad
.sp 1
.SH CONFORMING TO
POSIX.1-2001, POSIX.1-2008, C89, C99.
.PP
The C standards specify only the categories
.BR LC_ALL ,
.BR LC_COLLATE ,
.BR LC_CTYPE ,
.BR LC_MONETARY ,
.BR LC_NUMERIC ,
and
.BR LC_TIME .
POSIX.1 adds
.BR LC_MESSAGES .
The remaining categories are GNU extensions.
.SH SEE ALSO
.BR locale (1),
.BR localedef (1),
.BR isalpha (3),
.BR localeconv (3),
.BR nl_langinfo (3),
.BR rpmatch (3),
.BR strcoll (3),
.BR strftime (3),
.BR charsets (7),
.BR locale (7)
.SH COLOPHON
This page is part of release 5.13 of the Linux
.I man-pages
project.
A description of the project,
information about reporting bugs,
and the latest version of this page,
can be found at
\%https://www.kernel.org/doc/man\-pages/.
